Oil return device for ammonia systems



sept. 5, 1939. R. H. SWART 2,171,814

OIL RETURN DEVICE FOR AMMONIA SYSTEMS Filed Jan. 17, 1938 2' Sheets-$11661l l Sept. 5, 1939. R. H. sWART 2,171,814

OIL RETURN DEVICE FOR AMMONIA SYSTEMS Filed Jan. 17, 1938 2 Sheets-Sheet 2 Patented. Sept. 5, 1939 UNITED STATES PATENT OFFICE OIL RETURN DEVICE FOR AIVIIHONIA` SYSTEMS Application January 17, 1938, Serial No. 185,331

11 Claims. (Cl. 62-115) The invention relates to refrigeration and has reference more particularly to improved equipment for refrigerating systems using ammonia or other refrigerant liquids lighter than and immisciblein oil for removing the oil from the liquid refrigerant and short circuiting the same directly back into the crank case of the compressor.

It is necessary in the compression expansion types of refrigerating systems to properly lubricate the compressor. However, with proper lubrication of the compressor it is difficult to prevent the oil from travelling up the cylinder walls and passing over into the liquid line along with l5 the refrigerant. Various forms of traps have heretofore been used mostly in the hot gas discharge line between the compressor and condenser. Effective oil separation can not be produced atthis point because the oil is partially in the form of a very fine mist or spray which resists separation. As regards ammonia systems the oil is insoluble in the liquid refrigerant and will settle to the bottom when mixed therewith in much the same manner as water will in oil.

Accordingly. the invention contemplates separation of the oil from liquid ammonia by means of a trap located in the liquid line whereby the oil may be drawn off with or without some of the refrigerant. The present apparatus makes it possible to use plenty of oil for lubricating the compressor, notwithstanding that some of the oil may leave the compressor along with the refrigerant since this is separated and short circuited directly back into the crank case Of the compressor.

A more specific object of the invention is to provide improved means for ammonia refrigerating systems for separating the oil from the liquid refrigerant and which will be applicable to systems fed with a high side float, low side float, or

thermal expansion valve.

Another object is to provide oil removal means which Will remove oil from the liquid refrigerant by means of a by-pass circuit of 'refrigeration that may be automatically controlled by a thermal expansion valve.

With these and various other objects in view the invention may consist of certain novel features of construction and operation as will be more fully described and particularly pointed out in the specification, drawings and claims appended hereto.

In the drawings which illustrate an embodiment of the invention and wherein like reference characters are used to designate like parts- Figure 1 is a diagrammatic view illustrating the improvements of the invention as applied to an ammonia refrigerating system;

Figure 2 is a fragmentary enlarged view showing the yheader for the iiooded low side evaporat- 5 ing unit used in the refrigerating system of Figure 1; v

Figure 3 is a sectional View of the float and valve for the evaporating unit shown in Figure 2; 1

Figure 4 is a diagrammaticview illustrating a. modified form of oil return device showing the same applied to an ammonia refrigerating system; and

Figure 5 is also a diagrammatic view illustratl5 ing another modification for removing oil from the liquid refrigerant arid returning the same to -the compressor.

Referring to the drawings, the refrigerating system shown in Figure 1 includes the compressor indicated by the numeral I0 which is driven by the motor Il, the said compressor and motor being supported by the stand I2. The compressor has connection with the suction line I4 which delivers to said compressor gaseous refrigerant. 25 Said refrigerant upon leaving the compressor is at a high pressure and temperature and the same is thereby passed through the condenser I5 which may be of the air cooled or water cooled type. The lower end of the-condenser has connection with the liquid receiver I6 which forms a reservoir for the liquid refrigerant.

The king valve I8 fcontrols the iiow of the liquid refrigerant to the oil return device which, in accordance with the invention, includes the cylindrical container or trap 20 and the evaporating coil designated by numeral 2.I. The liquid line 22 connects with the bottom of the container 20 and at its other end joins with the expansion valve 23. The evaporating coil 2| is supplied 40 with refrigerant by said valve which is expanded during its travel through the coil, being eventually delivered as a gas to the suction line 24 having c'onnection with the main suction line I4 leading to the compressor. The expansion valve 23 is 45 thermostatically controlled by the bulb25 connecting with said Valve through the capillary tube 26.

The liquid line 28 leads from the upper end of the container 20 and connectswith the underside 50 of the header 30 of the main evaporator of the refrigerating system. As shown in Figures 2 and 3 the suction line I4 has connection with the top side of said header and also connecting with said header are a plurality of evaporating coils 3|. 55

One end of each coil joins with the header on the underside thereof, thereby providing an inlet; for

the liquid refrigerant. The other end of each" coil connects with the header' in the upper portion thereof in substantial alignment with the suction line I4 so that the returning gas from the several evaporating coils is conducted from the header by said suction line.

The evaporating unit above described is known as the flooded, low side type wherein the evaporating coils are flooded with liquid refrigerant, the supply of which to the header is controlled by the float 33 shown in Figure 3. The valve stem 34 secured to the float is pivotally supported by the standard 35, the said stem having connection at its free end with the valve 36. The liquid refrigerant supplied by line 23 is admitted to the header when the valve 36 is lifted from its seat 31. Such lifting of the valve will occur when the iioat 33 drops below a horizontal plane approximately coinciding with the center of the header 30. Accordingly,when the liquid level in the header is above said horizontal plane the float 33,

which is designed to iioat in liquid ammonia will actuate valve 36 to` close the same.

In the flooded or trapped type of evaporating unit it is necessary that the liquid refrigerant delivered to the evaporator be absolutely free of oil in order to insure eilicient operation of the system. The invention therefore contemplates interposing an oil trap'in the liquid line 23. In ammonia systems the oil is insoluble in the liquid refrigerant and thereforev any oil carried along with the liquid refrigerant will settle to the bottom of the container or trap 23. 'I'he oil and some liquid refrigerant will be conducted by the 1ine22 tothe thermostatic expansion valve 33. The refrigerant in its travel through the evapo-y rating coil 2| will be expanded. Said coil is a continuous, one pipe gravity return coil and therefore the return line 24 will deliver the gaseous refrigerant and also included therewith to the suction line I4 and thus to the compressor. The liquid line 23 has connection with the upper portion of lthe' container 20 and therefore the liquid refrigerant delivered to said line is free of oil.

An alternative construction applicable to the form of the .invention sho'wn in Figure 1 consists in substituting a single expansion valve for thel float controlled liquid refrigerant supply means shown. Such expansion valve is constructed to feed liquid refrigerant to the several coils 3i, and

a unit-of this nature is generally referred to as -the flooded, header type which also req'uires that the refrigerant supplied thereto be free of oil if satisfactory and efficient operation is to be secured. C Y

As a. result of the oil removing device ofthe invention the main evaporating unit is supplied with pure liquid refrigerant entirely free of oil and therefore, notwithstanding that said unit is of the flooded or trapped, low side type. high' operating eiiiciency is assured. All the oil and of. -course some liquid refrigerant is passed through the single evaporating coil 21| .which may be described as a by-pass circuit of refrigeration automatically operated by means of a thermal expansion valve for by-passing the oil and returningy the same to the compressor. In operation of the refrigrating system constructed as above described the thermal expansion valve 23 may be valvd to the receiver I6 or the trap 2li and therefore said expansion valve may be readily replaced without even stopping the refrigeration any oil that may be to the main evaporators. An added advantage I inherent in this construction is ther fact that an adequate high pressure lter may be put in the liquid line 22 leadingfrom the trap 20 to the said expansion valve, making it possible to' clean this oil to a high degree before setting it back to the compressor. The construction'also per-l mits the use of large scale traps or dirt accumulators in the main suction line without requiring means for returning any oil from them to the compressor.

In the modification shown in Figure 4 the king valve I8 controlling the flow of liquid refrigerant from the receiver I6 has connection through yline 39 to the cylindrical container or trap 40,

which, in combination with the evaporating coil 4I, comprises the oil return device of this modiiication. The liquid line 28 leads from the upper portion of the container 40 to the header 30 as described with respect to the refrigerating system of Figure 1. The main evaporating unit shown in Figure 4 is also of the flooded or trapped, low side type having a plurality of evaporating coils 3| connecting with said header which in turn has connection with the suction line I4, whereby the refrigerant gas is returned to the compressor.

'I'he liquid line 42 has connection with the bottom of the container 40 and leads to the thermal expansion valve 43, which delivers the liquid refrigerant in controlled amounts to the evaporating coil 4I. Said coil in this modification is in the form of a spiral and is located within the said container 40. 'I'he suction line 4,4 from said evaporating coil joins with the main suction line I4 and therefore the gaseous refrigerant and any oil that may travel along therewith will be returned to the compressor.

In this modification the refrigeration produced .liquid refrigerant which is fed as pure liquid refrigerant to the flooded low side evaporating unit. Also the coil 4I forms a by-pass circuit whereby the oil maybe by-passed to the compressor. In the modification of Figure 5 the refrigerating system is substantially the same as that described with respect to Figures 1 and 4. However, the container or oil return trap in this modification takes the form of a liquid receiver 50. The liquid refrigerant having oil mixed therewith is delivered to the receiver 50 by the pipe 5I having connection through the king valve I3 with the main liquid' receiver I6 of Athe compressor unit.

In the trap orreceiver 50 the oil suspended inv the liquid will gradually settle out and collect on the liquid level therein but does not come in contact with the oil. In other words, the end of said liquid line is located above the oil level in the trap or receiver 50. Thus, in operation the `oil is effectively removed from the liquid refrigerant and the same in substantially pure form is supplied to the line `28.

In accordance with the invention the oily level within the trap 50 isv maintained approximately constant by the float 52 which is designed to sink in liquid ammonia. but float in oil. of the valve stem 53 is piyotally supported by the support 54 and intermediate thereof said stem "carries, the valve 55. Movement of 'the valve 55 is effectively separated from the liquid refrigerant but instead of making use of a by-pass circuit of refrigeration there is substituted for said circuit an oil return line and float control means whereby oil in its pure form and without having mixed therewith any of the liquid refrigerant is sent directly back to the compressor.

What is claimed is:

l. An oil separation and return device for refrigeration systems using ammonia or other refrigerant liquids lighter than and immiscible in oil and including a compressor and a main evaporating unit, in combination, a trap located in the liquid line to the main evaporating unit for separating the oil from the liquid refrigerant, and an auxiliary evaporating coil having connection with said trap, said connection being constructed and arranged to feed the separated oil along with any liquid refrigerant in admixture therewith to said auxiliary evaporating coil, whereby the oil is returned to said compressor along with the expanded refrigerant from the auxiliary coil.

2. An oil separation and return devicev for refrigeration systems using ammonia or other refrigerant liquids lighter than and immiscible in Voil and including a compressor and a main evaporating unit, in combination, a trap located in the liquid line to the main evaporatingunit for separating the oil from the liquid refrigerant,

and an auxiliary evaporating unit having connection with said trap, said connection being constructed and arranged to feed the separated oil along with any liquid refrigerant in admixture therewith to said auxiliary evaporating unit, whereby theoil is returned to said compressor along with the expanded refrigerant from the auxiliary unit, said auxiliary unit comprising. a continuous coil of the non-trapped type.

3. An oil separation and return device for refrigeration systems having a compressor and a main evaporating unit of the iiooded or trapped low side type, in combination, a trap located in the liquid line to said evaporating unit for separating the oil from theliquid refrigerant, an auxiliary evaporating unit having connection with said trap,V said auxiliary unit comprising a continuous gravity return coil having an expansion valve, whereby the separated oil'from'the trap along with any liquid refrigerant in admixture therewith is fed to said auxiliary evaporating unit, said auxiliary unit connecting at its other end with the compressor and which thereby returns the oil to the compressor along with the expanded refrigerant from said auxiliary unit.

4. An oil separation return device for ammonia refrigeration systems having a compressor and a main evaporating unit of the flooded or trapped low side type, in combinatio a container located in the liquid line to said evaporating unit forming a trap for separating the oil from the liquid ammonia, said liquid line having connection with the upper portion of said container and thereby supplying to said evaporating unit pure liquid refrigerant, and an auxiliary evaporating unit having connection with the bottom of said containerwhereby the oil separated by the trap is delivered to said auxiliary evaporating unit along with any liquid refriger-ant in admixture therewith, said auxiliary unit comprising a continuous gravity return coil having an expansion valve and connecting at its other end with the compressor to thereby return the oil to the compressor along with the expanded refrigerant from said auxiliary unit.

5. An oil separation and return device for ammonia refrigeration systems having a compressor and a main evaporating unit of the flooded or trapped low side type, in combination, a container located in the liquid line to said evaporating unit forming a trap for separating the oil from the liquid ammonia, said liquid line having connection with the upper portion of s-aid container and thereby supplying to said evaporating unit pure liquid refrigerant, an auxiliary evaporating unit having connection with the bottom o f said container whereby the oil separated by said trap is delivered to said auxiliary evaporating unit along with any liquid refrigerant in admixture therewith, said auxiliary unit connecting at its other end with the compressor and thereby returning the oil to the compressor along with the expanded refrigerant from said auxiliary unit, and an expansion valve for said auxiliary evaporating unit for controlling the quantity of liquid refrigerant and also the quantity of oil fed thereto.l

6. An oil separation and return device for ammoni-a refrigeration systems having a compressor and a main evaporating unit of the flooded or trapped low side type, in combination, a container located in the liquid line to said evaporating unit forming a trap for separating the oil from theliquid ammonia, said liquid line having connection with the upper portion of said container and thereby supplying to said evaporating unit -pure liquid refrigerant, an auxiliary evaporating unit having connection with said trap whereby the oil separated by said trap is delivered to said auxiliary evaporating unit along with any liquid refrigerant in admixture therewith, said auxiliary unit comprising a continuous gravity return coil having connection at its other end with the compressor and which thereby returns oil to the compressor along with the expanded refrigerant from said auxiliary unit, and a thermostatically controlled expansion valve for said auxiliary evaporating unit having operation to control the quantity of liquid refrigerant and also the quantity of oil fed thereto.

7. An oil separating and return device for refrigeration systems of the compression-expansion type, in combination, a trap located in thel liquid line for separating the oil from the liquid refrigerant, and an auxiliary evaporating unit having connection with the bottom of said trap whereby the oil in said trap along with vany liquid refrigerant in admixture therewith'is delivered to said auxiliary unit, a portion of said unit having loc-a.- tion within the trap whereby the liquid refrigerant in the trap is maintained at a low temperature, and said auxiliary unit connecting at its other end with the compressor so-that the oil separated by the trap is returned to the compressor of the system along with the expanded refrigerant from said auxiliary unit.

8. An oil separation and return device for refrigeration systems having a compressor and a main evaporating unit of the flooded or trapped low side typ'e, in combination, a container located in the liquid line to said evaporating unit forming a trap for separating the oil from the liquid refrigerant, an auxiliary evaporating unit having connection with the bottom of said container whereby the oil in the trap along with any admixed liquid refrigerant is fed to said auxiliary unit, a portion of said auxiliary unit having location Within the container whereby the liquid refrigerant in the container is maintained at a low temperature, and said auxiliary unit connecting at its other end with the compressor so that the oil separated by the trap is returned to thec'ompressor along with the expanded refrigerant from said auxiliary unit.

9. An oilseparation return device for-refrigeration systemshaving a compressor and a main evaporating unit of the iiooded or trapped low `auxiliary evaporating unit, said auxiliary unit comprising a continuous gravity return coil provided with an expansion valve, a portion of said auxiliary unit having location Within 'the -container and said unit connecting at its other end with the compressor whereby the liquid refrigerant within the container is maintained at a low temperature and the .oil is returnedv to the compressor along with the expanded refrigerant from said auxiliary unit.

10. 'Ihe method of removing oi1,from liquid refrigerants lighter than and immiscible in oil, which consists in conducting the mixture of liquid refrigerant and oil to a quiescent chamber and separating the oil therefrom by gravity, conducting the pure liquid refrigerant to the evaporator of the refrigerating system, supplying said i oil and any liquid refrigerant admixed therewith to an auxiliary evaporating coil, expanding the refrigerant mixed with said oil in said auxiliary evaporating coil, and delivering said oil along with the expanded refrigerant to the suction line of the system, whereby the oil is eventually returned to the compressor of the system.

11. The method of operating a refrigerating system using a liquid refrigerant lighter than and immiscible in oil, which consists in conducting a. mixture of liquid refrigerant and oil to a quiescent chamber for separating the oil from said liquid refrigerant by gravity, conducting the pure liquid refrigerant to the evaporator of the system, supplying said oil along with any liquid 4 refrigerant in admixture therewith to an auxiliary evaporating coil, expanding the liquid re- 4 frlgerant mixed with the oil in said auxiliary evaporating coil, and delivering said oil along with the expanding refrigerant to the suction line of the system, whereby the oil is eventually returned to the'compressor of the system.

, RICHARD H. SWART. 

